Collapsible mandrel



April 7, 1953 Y R. G. BROWN 2,633,978

' COLLAPSIBLE MANDREL Filed April 12, 1949 w A V 1 w th XNVENTOR 21 I? um 1/ George Brown ATTORNEY Patented Apr. 7, 1 953 UNITED STATES PATENT OFFICE COLLAPSIBLE MANDREL Russell George Brown, Arnold, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Application April 12, 1949, Serial No. 86,881

by the die and bulb. The manufacturing setup is predicated upon round tube production, so that such round tube, after reduction to approximately the" desired wall thickness and diameter, forms the starting stock when production of square, oblong and other non-circular tube shapes is to be effected. Because of the excessive difference between the circumferenc'e'of the tube circle which will circumscribe a solid bulb defining one of such shapes and the perimeter thereof, it is usually necessary to employ a multiplicity of draw passes to efiect the change in shape instages so as to avoid folding or wrinkling of the tube wall during any one draw pass. This is particularly the case in connection with the formation of oblong tube shapes such as rectangles, ovals'an'd the like, since the I.D. of the roundstarting tube has to be greaterthan the major dimension of the oblong shaped bulb to permit the initial threading. With a tube only partially reshapedafter the first draw, extreme care "must 'be'exercised to assure that the tube, bulb and die aperture will not be angularly out of line with relation to each other for the succeeding draw. By the instant invention, the advantage of a sin gle draw pass is realized without folding or wrinkling by using a starting tube whose peripheral length is substantially the'same as the tube shape to be drawn therefrom and'pmviding a collapsible bulb to enable its introduction into.

the round starting tube.

' Another object of the invention is to provide a tube expanding mandrel or-bulb comprising a fixed body portion and a slidable bulb segment thereon, the'bulb being dimensionally contracted and expanded-by shifting the segment-rearwardly and iforwardly on the body portion, and the forward shifting of the segment into fully expanded position being completedby means of the tube blank as drawing thereof is initiated.

A further object is to provide an improvedeihpansible and collapsible bulb structure and -sim-" ple operating meanstherefor which will be. easy for the drawing of round ,tubing in a singledraw pass into a cross sectional shape having one of its dimensions greater than the inside diameter of theround tubing.

Other objects and advantages of the invention will be apparent from the following detailed description of presently preferred embodiments thereof, as illustrated on the accompanying drawings wherein: j

Fig. 1 is a side elevation of a portion of a draw bench incorporating the invention and illustrat ing the disposition of the mandrel or bulb op-- erating mechanism;

Fig.2 is a longitudinal section, on an enlarged scale, through the die and bulb mechanism showing the parts in tube drawing position;

Fig. 3 is a longitudinal section of the mecha nism of Fig. 2 taken on a plane at right angles thereto;

Fig, 4 is an end elevation looking from the exit or delivery side of the die in Fig. 2;

Fig. 5 comprises detail side, left and right end elevations, on an enlarged scale, of the central core of the bulb; a

Fig. 6 comprises detailside and end elevations of one of the movable bulb segments, on an enlarged scale, and

Fig.7 illustrates, in side elevation, a modification of the bulb of Fig. 2 and the manner of 1 threading a tube thereover. initially. j

The drawbench illustratedin Fig. 1 comprises longitudinally aligned mandrel, die, and drawv sections of any conventional. construction, the

mandrel and draw sections each being of such, length, as is customary, as will accommodate the desired length of tubes to be operated upon. The

framework of the mandrel section may comprise, as usual, a pair of'laterally spaced 1 channels 4 secured to a diecarrier frame or support 5 of the" die section and supported at intervalson suitable standards 6. Similarly, the draw sectionv may include a pair of laterally spaced channels 1 having secured to the upper flanges thereof.

track bars 8 on which a wheeled drawhead or tongs carriage 9' is adapted to travel. The die support 5 includesa die holderlil in which is mounted a removable die l I whose aperture is of the desired'cross-sectional shape, here shown as rectangular, through which a tube- 12 is adapted to be'drawn by means of the drawhead 9. drawhead is provided with the usual gripping jaws 13 with which to grip the pointed end of the tube projected through the die and also having a swinging hook [4 by means of which it is pted, to. be qpe iabl r nn e to 0 1 1 4 1 The ously travelling endless draw chain 15 of any suitable construction and disposed between the channels I slightly below the level of the track bars 8. The chain passes around an idler sprocket i6 adjacent the die and also around a driven sprocket (not shown) at the end of the draw section remote from the die.

Preliminary to drawing, the tube I2 is threaded or passed over a mandrel or bulb which cooperates with the die H in the drawing operation. The bulb, as shown in Figs. 2 through 6, comprises an elongated body or central core 26 and preferably a pair of bulb segments 2| slidably mounted thereon, although in some cases a single segment may be sufiicient. The core 28 is wedge shaped longitudinally to provide flat top and bottom inclined walls 22 and 23 on each oi which is formed a central upstanding longitudinal rib 24 having undercut sides to form a dovetail tenon. The underside 25 of each of the bulb segments 2| are likewise flat sided and formed with a longitudinal groove with undercut sides to form a dovetail mortise which mates with the dovetail tenon. The slope of the sides 25 of the segments 2 corresponds to the slope of the Walls 22 and 23 of the core 2.6, so that when the segments are assembled on the core from its small end they will have full bearing contact upon the core in transverse and longitudinal directions; This construction results in affording sliding movement or the segments on the core in an axial or longitudinal direction while providing pressure resisting engagement between the parts serving against crushing pressure normal to the axis to the bulb assembly during drawing and holding the segments against lateral shifting on the core.

Upstanding lugs or :stops :26 .are formed integrally on the big end of the core 20 to limit movement of the bulb segments .2] in the direction of draw. If desired, each segment, as shown, may be formed with a recess .23 in which a stop lug is received, the mutually engaging surfaces of the stop lugs and recesses being close fitting in order to aid in holding the segments against lateral shifting relative to thecore during a drawing operation.

The core 2i! is axially bored and threaded :for screw threaded attachment to :one end of a bulb rod 3%) by means of which the bulb assembly ,is adapted to be disposed in a fixed operating position in the draw .die. Other forms of attachment of bulb and rod are contemplated, it being necessary merely to efiect a positive securement with the small end of the bulb core facing the rod so that the rise of the sloping walls 22 and 23 is toward the exit or delivery side of the die. The segments may be slid by hand down these converging .or sloping sides 22- -23 toward the mandrel rod into retracted or collapsed -position, as shown in dotted lines .in Fig. 2, thereby reducing the major dimension of the oblong or rectangular shape defined by the core and segments when in expanded operating position against the stops 2-6, :as shown in full lines, to one that is smaller than the inside diameter of the round tube l2. Preferably the length of core '29 is more than twice the length of segments 21 so that the angularity of the sloping walls will not be excessively steep, here shown of about 6, but nevertheless suificient to cause the segments when in retracted position to lie below the level of the outer-most edges of the stops '26. As a result the tube 12 can easily be slid over the collapsed bulb preliminary to passing its pointed 4 end through the die aperture for gripping and drawing.

Any conventional means for securing and axially shifting the mandrel rod 30 may be employed. As here shown, the rear end of the rod is non-rotatably and slidably supported in an anchor 3i secured to channels 4 (Fig. 1) against which an enlargement or head on the rod is adapted to bear with the bulb in its fixed operating position in the die. This anchor may include usual adjusting means by which the position of the bulb with respect to the di may initially be established, not here illustrated as it forms no part of the instant invention. The bulb and rod are shifted rearwardly to clear the die when a tube l2 is to be threaded thereon for drawing. A ram 33, connected to shifting rod 34 operable by a handle 35 at the operator's station adjacent the die, may be advanced by longitudinal shifting of handle 35 in order to push the loaded bulb rod and its bulb forwardly into operating position in the die.

This motion advances the bulb core into position relatively to the die and to advance the segments 2] a pusher 36 movable on rod 30 is provided. The pusher is of bifurcated form for nesting of the core 20 therein and providing two forwardly projecting fingers 3] engageable with the respective segments 21. The pusher 3'! is fixed to an operating member 38 disposed in parallelism with the rod 30 and preferably in the form of a tube embracing the rod 30 for mutual support, to the rear end of which is secured an arm 39 holding it against rotation. Axial motion of the pusher rearwardly of core 29 is limited by suitable means such as :pin 40 so that the tips of fingers 31 will prevent accidental movement of the segments 2! off the small "end of the core 20. The arm 39 extends outwardly and downwardly and is secured, as by welding, to a shiftable tube 4| that is slidably mounted on one side of the framework 4, as by brackets 42, rod 34 preferably being slidably supported in the tube ii. A handle 43 is provided for tube 41, at the operators station, forward motion of which results in movement of pusher 36 towards the die, thereby pushing the segments 2! along the sloping sides 22-23 of "the core until the segments contact the inner wall of tube [2.

This contact is established before the segments reach their fully expanded or operating position by reason of the fact, as above pointed out, that for equal peripheries the long dimension of the rectangular bulb is greater than the inside diameter of tube 12, thus requiring outward displacement of the round tube wall by the segments .for them to reach operating position against stops 26. The operator is ;not required to move the Segments completely into operating position, instead .he starts the drawing operation by engaging hook 14 in draw chain IS, the jaws is automatically gripping the pointed tube end. As the drawhead .9 moves away from and pulls the tube through the die, the frictional engagement of tube 12 on the segments 2i and forcing pressure applied to them by the operator through the pusher mechanism causes the segments to initiate outward displacement of the tube wall. Thereafter the drag of the tube on the segments moves them into their operating position, the stops 26 sustaining the segments against movement beyond operating position.

It is to be observed that, once initiated, this power movement of the segments into operating position eilects gradual expansion of the tube 5. wall outwardly. .wliile Tithe 1' die effects inward displacementof the v tube, wall into contact. with the sides'of the bulb, danger f, folding or wrin kling being eliminated because'ofthe absence of excessive difference inamount of peripheral metal'between the round tube l2 and the :rectangular shaped tube l2a produced therefrom. Also as ;shown in Figs. 2 and 6, the rear outer edge ofgeach segment is relieved inwardly as indicated at 45, so as, to avoid'any danger of tearins. the. metal during displacement and drawing. Preferably, only a slight reduction in wall thicknessis effected during the draw so as to minimize metal pile up behind the die bearing and the resultant load on the bulb.

In Fig. 7, a self-energizing or automatic bulb structure is shown which is identical with that just described, except that pusher 36 and its associated operating mechanism is eliminated. In this form, a compression spring 41 is provided which encircles the, small or rod end of the core 20a behind the segments 2 la and is retained by a disk 48 clamped to the small end of the core by means of clamp nut 49 threaded on the bulb rod 30a. The end of spring 41 opposite disk 48 may or may not bear against the rear sides of the segments, as desired, when they are in operating position, it only being necessary that the spring be placed under compression by retractive movement of the segment axially to such position, as shown in dotted lines, as will permit the tube blank [2b to be passed thereover. In such position, the spring urges the segments into contact with the inside wall of the tube with such force that reversal of tube movement will cause the segments to move therewith. Subsequent to the threading of the tube over the bulb, when the bulb rod 30a is shifted forwardly toward the die by ram 33, the tube will be moved forwardly also and its pointed end projected through the die. Then when the draw is started, the bulb will be drawn up into operating position accompanied by axial movement of the segments against the positioning stops 260:.

In both forms of bulbs, the metal to metal contact between the segments and the bulb body prevents the formation of any flash on the interior of the drawn tubing. Both forms also may be used, if desired, to effect outward displacement of a portion of a tube wall without any change in shape of other portions or the remainder of the tube wall in the formation of tubing with a longitudinal rib projection, for example, since the retraction feature of the tube wall expanding segment permits easy passage of the proper size tube over the bulb preliminary to drawing. It is obvious, of course, that the bulb may have any other non-circular shape desired, itnot being limited to the specific rectangular shape illustrated.

It is further apparent that various changes may be made in the details of construction and the general form of the parts described without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

V 1. In a drawing apparatus for reshaping round tube to tube of oblong contour and substantially equal periphery, a collapsible bulb for cooperation with a draw die having an opening of oblong contour comprising an elongated bulb body disposed in a fixed operating position coaxially of said die during a drawing operation and having a longitudinal sloping wall rising toward and terminating adjacent the exit side of said die,

abulbisegment slidably secured onsaid wall, and a stop upstanding from said wall at the upper end thereof .to sustain said segment against movement beyond said operating position, said segment being movable inwardly on said sloping wall into retracted position for threading of said tube thereover preliminary to drawing and out-. wardly on said sloping wall into operating position againstlsaidstop, said bulb body and seementin operating position being of oblong contour having one dimension greater than thediameter of said tube, the rear outer edge of said segment. being. relieved inwardly, and a. segment moving member disposed to engage the rear side only of said segment and move the same toward said stop until said segment contacts the inner wall of said tube, whereby initial movement of said tube in drawing direction completes movement of said segment into operating position.

2. In a drawing apparatus for reshaping round tube to tube of oblong contour and substantially equal periphery, a collapsible bulb for cooperation with a draw die having an opening of oblong contour comprising an elongated, wedge-shaped body disposed in a fixed operating position within said die with its large end located adjacent the exit side of said die during a drawing operation and providing two opposite walls diverging in the direction of drawing, bulb segments of the same width as that of said body slidably secured on said diverging walls and integral stops upstanding from the upper ends of said walls, the rear outer edge of each segment being relieved inwardly, said segments being movable inwardly on said walls into retracted position for threading said tube thereover preliminary to drawing and outwardly on said walls to project outwardly from and abut said stops, and longitudinally movable pusher means incorporating forwardly projecting fingers disposed to engage the rear sides of said segments and move them toward said stops into contact at their relieved edges with the inner wall of said tube preliminary to drawing.

3. In a drawing apparatus for reshaping round tube to tube of oblong contour and substantially equal periphery, a collapsible bulb for cooperation with a draw die having an opening of oblong contour comprising an elongated, wedge-shaped body disposed in a fixed operating position within said die with its large end located adjacent the exit side of said die during a drawing operation and providing two opposite walls diverging in the direction of drawing, bulb segments of the same width as that of said body slidably secured on said diverging walls and integral stops upstanding from the upper ends of said walls, the rear outer edge of each segment being relieved inwardly, said segments being movable inwardly on said walls into retracted position for threading said tube thereover preliminary to drawing and outwardly on said walls to project outwardly from and abut said stops, and spring means disposed to engage the rear sides of said segments and yieldingly move them toward said stops into contact at their relieved edges with the inner wall of said tube preliminary to drawing.

4. In a drawing apparatus for reshaping round tube to tube of oblong contour and substantially equal periphery, a collapsible bulb comprising an elongated, wedge-shaped body having two opposite walls diverging in the direction of drawing, bulb segments of the same width as said body secured on said diverging walls and slidable thereon between a rearward retracted position for threading said tube thereover preliminary to aasaors.

drawing and a forward extended operating position, and integral stops at the forward ends of said walls, the rear outer edge of each segment being relieved inwardly, said segments in forward extended position abutting said stops and defining with said body an oblong bulb having one dimension greater than the diameter of said tube, and segment moving means disposed to engage the segments and move them toward said stops into contact at their relieved edges with the inner wali of said tube, whereby initial movement of said tube in the drawing operation completes movement of said vsegmemts into operating position.

RUSSELL GEORGE 'BROVVN.

8 BEFERENGES 0min The following references are of record in the file of thispatent:

UNITED STATES PATENTS 2,234,863 Heetkamp .---.V-- Mar. 131, 1941 

